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Author Topic: FSK31 vs PSK31 for polar flutter?  (Read 4853 times)
KF6IIU
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Posts: 299




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« on: December 18, 2002, 04:19:37 PM »

Has anyone tried FSK31? I wonder if it would be more resistant to polar flutter than PSK31. From the West Coast, PSK31 is pretty useless for paths to Europe and Russia. I've tried signing "DE KF6IIU FSK31 FSK31" in morse but so far no takers.

I can't run MFSK16 - I use an FT-101E and its not stable enough. RTTY is pretty resistant to polar flutter; I've had fun with it and gotten some good contacts.

Listen for me about 0600Z on 14070 when UA's are CQing the US -
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KF6IIU
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Posts: 299




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« Reply #1 on: December 18, 2002, 08:52:36 PM »

Well, forget about it for now - operating PSK31 seems so hard on my FT-101 regardless of the power level I think I'm going to skip the digital modes until I get a newer rig. It's weird - even limiting the plate current to 150 ma (1/2 or recommended) and at about 25 W - I can hear the finals "plink" as they get thermally stressed.

However, I did notice FSK31 did not cause my RF power meter to jump around like it does during PSK31. FSK31 doesn't have that "spike" in the signal from the phase change.

See you all on SSB and gool old fashioned CW for now...
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NB6Z
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« Reply #2 on: December 19, 2002, 07:13:01 PM »

FSK should not be any harder on your rig than RTTY or MFSK16...
To answer your question, FSK31 is no better for polar distortion than psk31 because the DSP tuning at 32 hz signal width is just as critical. (A new version called FSK63 is in the works for MixW and will address some of these issues that make psk31 poor when phase distortion occurs.) FSK does not have the issue of IMD like PSK, because only one carrier is present instead of 2, (maybe this is why you think it is "harder" on your rig). MFSK16 is the best digi mode to work through flutter and other band crap! Your FT-101 will probably do well with Feld Hell mode which is also good for flutter if you can find a DX station who uses it these days. Stability is not critical for Hell modes since they are not really digital in terms of data bits and bytes.
Get a low cost stable rig (like an FT-840) and CU on the digi bands.
73 Griff.
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KF6IIU
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Posts: 299




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« Reply #3 on: December 21, 2002, 08:53:58 PM »

Thanks for the advice - might give Hell a try and see what happens.

It must be something about the FT-101 - but PSK31 seems to really make it unhappy, even at minuscule power levels. I have a feeling it's the very long duty cycles that tend to occur. And, compared to RTTY, there are still "phase transitions" that occur even when the keyboard is idle - RTTY just sits there on carrier IIRC when you are not typing something.

Actally, I've been thinking of returning to the oldest digital mode of all - CW. It's been a while...
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N3HKN
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Posts: 243




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« Reply #4 on: January 22, 2003, 06:34:50 AM »

You may want to think in terms of parasitics exposed by the digital transitions.
Dick N3HKN
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